Othello's suffering results mostly from his poor judgment. He trusts the wrong people and mistrusts those who are most loyal to him (Desdemona and Cassio). In Act 3, he sets aside his sensible, military side and falls prey to Iago's manipulation.

It must be noted in Othello's case, though, that while he might share Brutus's tragic flaw (from Julius Caesar), Othello deserves more sympathy from the audience. In a sense, he is a victim of his time period. While Brutus exercised poor judgment throughout Julius Caesar, he was used to commanding respect because of his family and character and did not have to fight against prejudice. In contrast, Othello's poor judgment largely results from his self-doubt regarding his true acceptance into European society. He has been conditioned to think that he is not good enough for Desdemona or the inner sanction of white society.

While some argue that Othello's tragic flaw is jealousy, he really does not suffer from that until Iago plants seeds of doubt in his heart regarding Desdemona. Normally, Shakespeare's tragic characters establish a pattern connected to their tragic flaws, and there really is no pattern to justify jealousy as a flaw with which Othello has constantly struggled.

Othello's tragic flaw is the importance he places in his honour and reputation. Othello falls for Iago's lies easily because he cannot stand the mere thought of his reputation being marred. Whether Desdemona has cheated on him or not, then becomes somewhat secondary, because only the possibility of her cheating is enough for Othello.

Othello believes that his reputation defines his personality. That's why he takes it so seriously because without his honour he's nothing.

This becomes his tragic flaw. A tragic hero is an essentially good man who makes a mistake that the audience can sympathise with. Only a good and noble man would have place so much importance in his reputation. Thus, Othello's honour becomes his weakness.